Redknapp worked on the deal in 2012 that would bring Vertonghen to Spurs that summer, before being replaced by Andre Villas-Boas prior to the Belgian signing.
"It must be tough [for someone in Jan's situation]," Redknapp told the London Evening Standard. "He's a fantastic player. We agreed to sign him when I was in charge. I watched him play on several occasions.
"I knew he was going to be a top player, and I'm sure he'll settle back in at Tottenham and have a good season next year."
For the big stories and the banter follow us on Twitter: @tribalfootball